Progressive force electro-permanent magnets actuator

ABSTRACT

An example system includes a disk that is rotatable and has a plurality of ferromagnetic elements disposed in a radial array on a surface of the disk; and at least one electro-permanent magnet (EPM) mounted adjacent to the disk such that a gap separates the disk from the EPM. Applying an electric pulse to the at least one EPM changes a magnetic state thereof, thereby generating an external magnetic field that traverses the gap between the disk and the EPM and interacts with a ferromagnetic element of the plurality of ferromagnetic elements, and causing a rotational speed of the disk to change as the disk rotates.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional patentapplication Ser. No. 62/428,013, filed on Nov. 30, 2016, and entitled“Progressive Force Electro-Permanent Magnets Actuator,” which is hereinincorporated by reference as if fully set forth in this description.

BACKGROUND

The term “brake” may refer generally to a mechanical device or systemthat may constrain a moving system by absorbing energy therefrom. It isused for slowing or stopping a moving object, wheel, axle, or to preventits motion. In many brake systems, the operation of absorbing energy isaccomplished via means of friction, which might cause component wear andgenerate heat.

SUMMARY

The present disclosure describes embodiments that relate to aprogressive force electro-permanent magnets actuator.

In one aspect, the present disclosure describes a braking system. Thebraking system includes a first disk that is fixed and has one or moreEPMs disposed in a radial array on a surface of the first disk; and asecond disk rotatably mounted adjacent to the first disk such that a gapseparates the second disk from the first disk. The second disk has aplurality of ferromagnetic elements disposed in respective radial arrayon a respective surface of the second disk. Applying an electric pulseto at least one EPM of the one or more EPMs changes a magnetic state ofthe EPM, thereby (i) generating an external magnetic field thattraverses the gap between the first disk and the second disk andinteracts with a ferromagnetic element of the plurality of ferromagneticelements, and (ii) causing a rotational speed of the second disk tochange as the second disk rotates.

In another aspect, the present disclosure describes a braking systemthat includes a disk that is rotatable and has a plurality offerromagnetic elements disposed in a radial array on a surface of thedisk; and at least one electro-permanent magnet (EPM) mounted adjacentto the disk such that a gap separates the disk from the EPM. Applying anelectric pulse to the at least one EPM changes a magnetic state thereof,thereby (i) generating an external magnetic field that traverses the gapbetween the disk and the EPM and interacts with a ferromagnetic elementof the plurality of ferromagnetic elements, and (ii) causing arotational speed of the second disk to change as the disk rotates.

In still another aspect, the present disclosure describes an actuator.The actuator includes a piston; a stop element; and a series ofelectro-permanent magnets (EPMs). The series of EPMs includes at least afirst EPM and a second EPM. The series of EPMs is constrained betweenthe piston and the stop element. Each EPM may be switched between (i) anactivated state in which the EPM exhibits an external polarized magneticfield and (ii) a passive state in which the EPM does not exhibit anexternal polarized magnetic field. The first EPM and second EPM arearranged such that when both the first EPM and the second EPM are in theactivated state, a magnetic pole of the first EPM is adjacent to the alike magnetic pole of the second EPM, and the first EPM and the secondEPM exhibit a repulsive force between them causing a motive force on thepiston away from the stop element. When both the first EPM and thesecond EPM are in the passive state, they do not exhibit a repulsiveforce between them and do not cause a motive force on the piston awayfrom the stop element.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates an electro-permanent magnet in an “ON”configuration, in accordance with an example implementation.

FIG. 1B illustrates the electro-permanent magnet of FIG. 1A in an “OFF”configuration, in accordance with an example implementation.

FIG. 2A illustrates an alternative configuration for anelectro-permanent magnet, in accordance with an example implementation.

FIG. 2B illustrates operation of the electro-permanent magnet shown inFIG. 2A, in accordance with an example implementation.

FIG. 3 illustrates an actuator having electro-permanent magnets, inaccordance with an example implementation.

FIG. 4 illustrates an actuator with electro-permanent magnets having adifferent orientation compared to the electro-permanent magnets shown inFIG. 3, in accordance with an example implementation.

FIG. 5 illustrates a side view of a braking system, in accordance withan example implementation.

FIG. 6 illustrates a braking system with ferromagnetic elementsconfigured as permanent magnets, in accordance with an exampleimplementation.

FIG. 7 illustrates a braking system with ferromagnetic elementsconfigured as electro-permanent magnets, in accordance with an exampleimplementation.

FIG. 8 illustrates a braking system with a first disk being offsetrelative to a second disk, in accordance with an example implementation.

FIG. 9 illustrates a braking system 900, in accordance with an exampleimplementation.

FIG. 10 illustrates a braking system with an axis of a first disk beingperpendicular to an axis of rotation of a second disk, in accordancewith an example implementation.

DETAILED DESCRIPTION

The following detailed description describes various features andfunctions of the disclosed systems with reference to the accompanyingfigures. The illustrative system and apparatus embodiments describedherein are not meant to be limiting. It may be readily understood thatcertain aspects of the disclosed systems and methods can be arranged andcombined in a wide variety of different configurations, all of which arecontemplated herein.

Further, unless context suggests otherwise, the features illustrated ineach of the figures may be used in combination with one another. Thus,the figures should be generally viewed as component aspects of one ormore overall implementations, with the understanding that not allillustrated features are necessary for each implementation.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to skill in theart, may occur in amounts that do not preclude the effect thecharacteristic was intended to provide.

I. Overview

An actuator is a component of a machine that is configured for moving orcontrolling a mechanism or system. The actuator may be coupled to anenergy source (e.g., electric power, pressurized hydraulic fluid or gasfrom a pump). For the actuator to operate, it receives a control signalfrom a controller, and then the actuator responds by converting theenergy from the source of energy into mechanical motion. As the actuatormoves, it may apply a particular force having a magnitude is based onthe level of energy supplied by the energy source. The control signalcould be relatively low energy and may be electric voltage or current,pneumatic or hydraulic pressure, or even human power.

In some examples, it may be desirable to apply a force of varyingmagnitudes based a given input. For instance, the actuator could becoupled to a brake pad, and it may be desired to apply different brakingforces based on a speed of an object being slowed down or some otherinput. However, in these examples, larger amount of energy are suppliedfrom the energy source to applying larger forces. Hence, an actuatorthat can apply forces of varying or progressive magnitude, while improveefficiency and reducing energy consumption can be beneficial.

Disclosed herein are apparatuses and systems that involve usingelectro-permanent magnets in an actuator to apply progressive forceswhile reducing energy consumption.

II. Example Electro-Permanent Magnets

An electro-permanent magnet (EPM) is a type of magnet that includes bothan electromagnet and a dual material permanent magnet. A magnetic fieldproduced by the electromagnet is used to change the magnetization of thepermanent magnet. In an example, the permanent magnet includesmagnetically soft and hard materials, where the soft material has lowermagnetic coercivity compared to the hard material and can thus have itsmagnetization changed. When the magnetically soft and hard materialshave opposite magnetizations, the EPM has no net field, and when theyare aligned, the EPM generates an external polarized magnetic field.

FIG. 1A illustrates an EPM 100 in an “ON” configuration, and FIG. 1Billustrates the EPM in an “OFF” configuration, in accordance with anexample implementation. The EPM 100 includes two permanent magnets 102and 104 connected by u-shaped elements 106 and 108.

The elements 106 and 108 could be made, for example, of a high magneticpermeability material or iron alloy such as magnet steel. As an example,the elements 106 and 108 could be made of Hiperco®, which includes aniron-cobalt-vanadium soft magnetic alloy that exhibits high magneticsaturation (24 kilogauss), high direct current maximum permeability, lowdirect current coercive force, and low alternating current core loss.However, other materials could be used.

The permanent magnet 102 is a low coercivity magnet. As an example, thepermanent magnet 102 could include an iron alloy, which in addition toiron, may include aluminum (Al), nickel (Ni) and cobalt (Co), and thusthis iron alloy may be referred to by the acronym AlNiCo. The permanentmagnet 104 is a high coercivity magnet. As an example, the permanentmagnet 104 could include N40 grade rare-earth magnets such as aneodymium magnet, also known as NdFeB, NIB or Neo magnet, which is arare earth permanent magnet made from an alloy of neodymium, iron andboron. Both example materials, i.e., NdFeB and AlNiCo, may have the sameremanence (around 1.3 Teslas) but AlNiCo has a lower intrinsiccoercivity of 50 kiloamperes/meter (kA/m) while NdFeB has an intrinsiccoercivity of 1120 kA/m. In the description provided herein AlNiCo andNdFeB are used as examples of materials for the permanent magnets 102and 104; however, other materials could be used where one magneticmaterial has a lower coercivity than the other.

A coil 110 is wound around the permanent magnet 102. The coil 110 isdesigned such that if an electric pulse (e.g., electric current orvoltage pulse) of sufficient power and duration is provided through thecoil 110 in one direction, the generated magnetic field will be higherthan the intrinsic coercivity (H_(ci)) of the permanent magnet 102, andcan thus change is magnetic state or magnetization. In this case, thepermanent magnet 102 will be magnetized in the direction of the fieldinside the coil 110. Applying an electric pulse in the oppositedirection will lead to magnetize the permanent magnet 102 in theopposite direction.

For example, if the permanent magnet 102 is magnetized such that thenorth pole (N) of both permanent magnets 102 and 104 are pointing in thesame direction (e.g., up in FIG. 1A), the magnetic configuration of FIG.1A is obtained. Particularly, the element 106 would have two magneticnorths at its ends and the element 108 would have two magnetic souths(S) at its ends. In this case, the element 106 may operate as a northpole of the EPM 100, and the element 108 may operate as a south pole ofthe EPM 100. Further, the element 106 may concentrate generated magneticflux lines 112, but might not contain the magnetic flux, and thus themagnetic flux will flow externally through the air (or other externalmedium) seeking the element 108 (magnetic south). In this configuration,the EPM 100 may be referred to as being in an “ON” or activated state.

Applying an electric pulse through the coil 110 in the oppositedirection magnetizes the permanent magnet 102 in the opposite direction.Thus, in this case, the element 106 would have a north pole (N) at oneend and a south pole (S) at the other end, whereas the element 108 hasopposite poles at its ends compared to the element 106 as illustrated inFIG. 1B. In this configuration, the magnetic flux lines 112 may beconcentrated inside both elements 106 and 108 creating a closed circuitfor the magnetic field because of the high permeability of the iron.However, no external magnetic field is generated and the EPM 100 may bereferred to as being in an “OFF” or passive state. In this manner, usingan electric pulse through the coil 110, the magnetic state of the EPM100 can be switched between the “ON” and “OFF” states.

The terms “ON state” and “activated state” are used hereininterchangeably. Also, the terms “OFF state” and “passive state” areused herein interchangeably.

Although FIGS. 1A-1B illustrate the coil 110 wound around the permanentmagnet 102, but not the permanent magnet 104, in other exampleconfigurations, the coil 110 could be wound around both permanentmagnets 102 and 104. As long as one of the magnets has lower intrinsiccoercivity than the other, and the power of the electric pulse is lessthan a particular threshold, the magnetization direction of the magnetwith lower coercivity would flip without changing the other's directionof magnetization assuming the power and duration.

FIG. 2A illustrates an alternative configuration for an EPM 200, inaccordance with an example implementation. As shown in FIG. 2A, the EPM200 includes a first permanent magnet 202 made of, for example, AlNiCOand a permanent magnet 204 made of, for example, NdFeB. The permanentmagnets 202 and 204 are disposed between keepers or elements 206 and 208(made from magnet steel or Hiperco®, for example) configured to hold thepermanent magnets 202 and 204 and concentrate magnetic flux lines. Thepermanent magnets 202 and 204 could be substantially parallel to eachother. The permanent magnet 202 is shown disposed below the permanentmagnet 204; however, other configurations are possible.

A coil 210 is wound around both permanent magnets 202 and 204. The coil210 is designed such that if an electric pulse of sufficient power andduration is provided therethrough, the generated magnetic field will behigher than the intrinsic coercivity (H_(ci)) of the first permanentmagnet 202, but not the second permanent magnet 204. Thus, magnetizationof the first permanent magnet 202 may change, while magnetization of thesecond permanent magnet 204 remains unchanged.

When the EPM 200 is in the “ON” state with both permanent magnets 202and 204 magnetized in the same direction, the generated externalmagnetic field traverses a gap 212 and interacts with a target object214. Particularly, if the target object is made of a ferromagneticmaterial (e.g., magnet steel), then the generated external magneticfield may cause the target object 214 to be attracted to the EPM 200 andspecifically to the elements 206 and 208.

In some examples, the target object 214 could include a permanent magnetor another EPM. Also, in FIG. 2A, the elements 206 and 208 protrudebeyond the permanent magnets 202 and 204 so as to attract the targetobject 214 thereto without the target object 214 interfering with thepermanent magnets 202 and 204. In other examples, however, the elements206 and 208 could be made shorter as shown below with respect to FIGS.3-7.

FIG. 2B illustrates operation of the EPM 200 in conjunction with thetarget object 214, in accordance with an example implementation. FIG. 2Billustrates the EPM 200 in four states: A, B, C, and D. State Aillustrates the EPM 200 in the “OFF” state, state B illustratesswitching on the EPM 200, state C illustrates the EPM 200 in the “ON”state, and state D illustrates switching off the EPM 200. Referencenumerals for the permanent magnets 202 and 204, the elements 206 and208, the coil 210, the gap 212, and the target object 214 are shown instate A, but not the other states of FIG. 2B to reduce visual clutter inthe drawing.

In the “OFF” state shown in state A, the two permanent magnets 202 and204 are oppositely polarized, and thus the resulting magnetic fluxcirculates inside the EPM 200, and no magnetic force acts on the targetobject 214. When a positive electric pulse 216 is provided through thecoil 210 as shown in state B, a clockwise magnetic flux is imposedthrough the first permanent magnet 202 thus magnetizing it rightwardsuch that both permanent magnets 202 and 204 are magnetically polarizedin the same direction. As a result, the magnetic field of the firstpermanent magnet 202 reinforces the magnetic field of the secondpermanent magnet 204 and an external polarized magnetic fieldrepresented by flux line 218 is generated. The element 206 operates as anorth pole (N) and the element 208 operates as a south pole (S). Theexternal magnetic field traverses the gap 212 and attracts the targetobject 214 toward the EPM 200.

The EPM 200 remains in the “ON” state even when the electric pulse 216ends as shown in state C. Therefore, the EPM 200 is distinguished fromelectromagnets in that the EPM 200 may remain in the “ON” state withouta continuous current through the coil 210. Thus the EPM 200 operateswith a reduced power consumption compared to electromagnets.

When a negative electric pulse 220 is provided through the coil 210 asshown in state D, a counter-clockwise magnetic field represented by fluxline 222 is imposed through the first permanent magnet 202 thusmagnetizing it leftward such that the two permanent magnets 202 and 204are oppositely polarized. The external magnetic field represented by theflux line 218 in state B then decays and disappears, and no magneticforce acts on the target object 214. Thereafter, the EPM 200 revertsback to the “OFF” state illustrated in state A.

III. Example Progressive Force EPM Actuators

EPMs could be used to enable an actuator to apply a varying force whileusing a reduced amount of power compared to other actuators. Theactuator could, for example, be used in a braking system. The brakingsystem may involve a brake pad contacting a moving object to slow itdown. However, in other configurations, EPMs may enable slowing down amoving object while reducing or eliminating friction as described belowwith respect to FIGS. 5-10.

FIG. 3 illustrates an actuator 300 having EPMs, in accordance with anexample implementation. The actuator 300 includes a series of EPMs suchas EPMs 302A, 302B, 302C, 302D, and 302E. Five EPMs are used here as anexample for illustration only, and more or fewer EPMs could be used. TheEPMs 302A-E are disposed in series on a surface 304. In other examples,the EPMs could be disposed within a tube or other structure.

The EPMs 302A-E could, for example, be similar to the EPM 200 describedabove. For instance, the EPM 302A includes a first element 306, a secondelement 308, and a coil 310 that surrounds two permanent magnets similarto the permanent magnets 202 and 204. The permanent magnets are notshown to reduce visual clutter in the drawings. For example, theelements 306 and 308 correspond to the elements 206 and 208,respectively. The other EPMs 302B-E may have similar components andstructure as the EPM 302A.

The EPMs 302A-E are disposed such that when any two consecutive EPMs,such as EPM 302A and 302B, are switched to the activated or “ON” state,both EPMs exhibit an external polarized magnetic field such that likepoles of the EPMs face each other or are adjacent to each other, and theEPMs are repelled away from each other. In an example, the EPMs 302A-Emay be disposed such that the EPMs contact each other. However, in otherexamples, the EPMs could be disposed such that gaps separate them. Inanother example, the gaps could include compliant material disposedbetween the EPMs.

The actuator 300 may include a stop element 312 at one end of the seriesof EPMs 302A-E configured to precluded the EPM 302A from repellingbeyond a particular location of the stop element 312. Further, the EPM302E disposed at the other end of the series of EPMs 302A-E may becoupled to a piston 314. In an example, the EPM 302E may be integratedinto the piston 314. In this configuration, the series of EPMs aredisposed between the piston 314 and the stop element 312.

In an example, the stop element 312 could be a hard-stop. In anotherexample, a compliant material 315 (e.g., a spring, rubber, or elasticmaterial that can absorb kinetic energy of the EPM 302A) could bedisposed between the stop element 312 and the EPM 302A.

Switching two or more of the EPMs 302A-E to the activated or “ON” statemay cause a cascading motion of the EPMs 302A-E, thus causing the piston314 to move. As an example, if the EPMs 302A and 302B are both switchedto the “ON” state by sending an electric pulse to their coils, the southpole (S) of the EPM 302A faces the south pole (S) of the EPM 302B.Consequently, a repulsive force is generated between the EPMs 302A and302B, and they may be repelled away from each other. The EPM 302A mightnot translate beyond the stop element 312 or the complaint material 315,and therefore the EPM 302B may be repelled in a direction of arrow 316(rightward in FIG. 3). Particularly, the EPM 302B moves toward the EPM302C. If the EPM 302C is in the passive or “OFF” state, then the EPM302B may push the EPM 302C toward the EPM 302D. The EPM 302C may thenpush the EPM 302D toward the EPM 302E. The EPM 302D may then push theEPM 302E and cause it to move along with the piston 314 coupled theretoin the direction of the arrow 316A (rightward in FIG. 3). In thismanner, the repulsive force between the EPMs 302A and 302B generated amotive force that pushes the piston 314 away from the stop element 312.

Thus, switching the EPMs 302A-B to the “ON” state caused a cascadingmotion of the EPMs 302A-E, thus applying a force to the piston 314 andcausing it to move. A magnitude of the force applied to the EPM 302E andthe piston 314, and thus the force that could be applied by the piston314 on another object, may be dependent on how many of the EPMs 302A-Eare switched to the “ON” state. If one or more EPMs are switched to the“ON” state in addition to the EPMs 302A and 302B, the repulsive forcesgenerated and thus the motive force on the piston 314 may increase. Forexample, if the EPM 302C is switched to the “ON” state such that itsnorth pole (N) faces or is adjacent to the north pole (N) of the EPM302B, then the EPM 302C may be repelled away from the EPM 302B, which isrepelling away from the EPM 302A. As such, the force applied to the EPM302C causing it to move in the direction of the arrow 316 may be larger.For instance, the force applied to the EPM 302C may be an aggregation ofthe force with which the EPM 302B is repelled from the EPM 302A and theforce with which the EPM 302C is repelled from the EPM 302B. As aresult, the force that is applied to the piston 314 may increasecompared to if the EPM 302C is not switched to the “ON” state.

Similarly, if the EPM 302D is switched to the “ON” state such that itssouth pole (S) faces or is adjacent to the south pole (S) of the EPM302C, then the EPM 302D may be repelled away from the EPM 302C. At thesame time, the EPM 302C is repelling away from the EPM 302B, which isrepelling away from the EPM 302A. As such, the force applied to the EPM302D causing it to move in the direction of the arrow 316 may be larger.As a result, the force that is applied to the piston 314 may increase.

Further, if the EPM 302E is switched to the “ON” state such that itsnorth pole (N) faces or is adjacent to the north pole (N) of the EPM302D, then the EPM 302E may be repelled away from the EPM 302D. At thesame time, the EPM 302D is repelling away from the EPM 302C, which isrepelling away from the EPM 302B, which in turn is repelling away fromthe EPM 302A. As such, the force applied to the EPM 302E causing it tomove in the direction of the arrow 316 may be larger. As a result, theforce that is applied to the piston 314 may increase.

In this manner, the force applied to the piston 314 causing it to movein the direction of the arrow 316 may be progressively increased byprogressively switching more EPMs to the “ON” state. The larger thenumber of EPMs in the “ON” state, the larger the magnitude of the forceapplied to the piston 314, thus also the larger the force that thepiston 314 applies to other objects.

When the EPMs are switched back to the passive state of “OFF” state,they do not exhibit a repulsive force between them and do not cause amotive force on the piston 314 away from the stop element 312.

In some example implementations, a subset of the EPMs 302A-E could bereplaced with permanent magnets. In these implementations, a permanentmagnet that is replacing a particular EPM may have the particularpolarity of the EPM shown in FIG. 3 when the EPM is switched to the “ON”state. For instance, a permanent magnet may be disposed between twoEPMs. As a specific example, the EPMs 302B and 302D could be replacedwith permanent magnets.

In the example where gaps separate the EPMs 302A-E from each other, theEPMs that are in the “ON” state may operate as if there is a spring thatcouples them to each other. However, the spring in this case is amagnetic spring that has an effective spring rate, which may depend onthe number of EPMs in the “ON” state, dipole moment, and the gapsbetween the respective EPMs. In this case, the force that one EPMapplies to a neighboring EPM while both of which are in the “ON” statemay increase as the gap therebetween decreases.

The actuator 300 may include a spring 318 that couples the piston 314 toa fixed structure or element 320. In this configuration, the spring rateof the spring 318 is such that the force resulting from one or more ofthe EPMs 302A-E being switched to the “ON” state could overcome theforce of the spring 318 to move the piston 314. When the EPMs that arein the “ON” state are switched back to the “OFF” state, the spring 318retracts the piston 314 in a direction opposite to the direction of thearrow 316 (leftward in FIG. 3). To preclude oscillations that could becaused by the spring 318, the actuator 300 may include stop elements322A and 322B that prevents the piston 314 from moving leftward beyondthe location of the stop elements 322A and 322B. In another example, adamping device may be coupled to the spring 318 so as to mitigate orprevent oscillations of the piston 314.

In an example, the actuator 300 may operate as a brake actuator. In thisexample, a braking pad 324 may be coupled to the piston 314. As thepiston 314 moves, the braking pad 324 may come in contact with a movingobject 326. The moving object 326 could be moving linearly (e.g., up anddown) or may be a rotary object. When the braking pad 324 contacts themoving object 326, the resulting friction therebetween dissipates thekinetic energy of the moving object 326 and slows it down. The magnitudeof the braking force may be based on the number of the EPMs 302A-E thatare switched to the “ON” state.

Different configurations could be used in the actuator 300. For example,as mentioned above, a subset of the EPMs 302A-E could be replaced bypermanent magnets. In an example, the EPM 302E or the piston 314 may bea permanent magnet. In an example implementation, one EPM and a onepermanent magnet could be used. Either the EPM or the permanent magnetcould be coupled to the piston 314. Switching the EPM to the “ON” statemay repel the EPM away from the permanent magnet thus causing motion ofthe piston 314. Other example implementations are possible.

FIG. 4 illustrates an actuator 400 with EPMs 402A-E having a differentorientation compared to the EPMs 302A-E, in accordance with an exampleimplementation. Particularly, the EPMs 402A-E are disposed such thatwhen any two consecutive EPMs, such as EPMs 402A and 402B, are switchedto the “ON”, both poles of each EPM face or are adjacent to like polesof the neighboring EPM such that the EPMs are repelled away from eachother. For instance, as shown in FIG. 4, if the EPMs 402A and 402B areswitched to the “ON” state, the north pole (N) of the EPM 402A faces oris adjacent to the north pole (N) of the EPM 402B. Similarly, the southpole (S) of the EPM 402A faces or is adjacent to the south pole (S) ofthe EPM 402B. In this configuration, the repulsive force between twoconsecutive EPMs in the “ON” state may be higher than the respectiverepulsive force that results in the configuration of FIG. 3. The higherforce results because the two poles are repelling the EPMs from eachother compared to one pole in the configuration of FIG. 3.

In examples, the EPMs 402A-E could be contacting each other as shown inFIG. 4 or could have compliant material disposed therebetween. However,in other examples, the EPMs 402A-E may be disposed such that respectivegaps separate the EPMs 402A-E. The actuator 400 may include the stopelement 312 disposed at one end of the series of EPMs 402A-E andconfigured to preclude the EPM 402A from repelling beyond a particularlocation of the stop element 312. The EPM 402E disposed at the other endof the series of EPMs 402A-E may be coupled to the piston 314. In anexample, the EPM 402E may be integrated into the piston 314

Similar to the configuration of FIG. 3, switching two or more of theEPMs 402A-E may cause a cascading motion of the EPMs 402A-E, thuscausing the piston 314 to move. For example, if the EPMs 402A and 402Bare both switched to the “ON” state by sending an electric pulse totheir coils, the south pole (S) of the EPM 402A faces the south pole (S)of the EPM 402B, and the north pole (N) of the EPM 402A faces the northpole (N) of the EPM 402B. Consequently, the EPMs 402A and 402B exhibit arepulsive force therebetween that pushes them away from each other. TheEPM 402A might not translate beyond the stop element 312 or thecomplaint material 315, and therefore the EPM 402B may be repelled inthe direction of the arrow 316 (rightward in FIG. 4). Particularly, theEPM 402B moves toward the EPM 402C. If the EPM 402C is in the “OFF”state, then the EPM 402B may push the EPM 402C toward the EPM 402D. TheEPM 402C may then push the EPM 402D toward the EPM 402E. The EPM 402Dmay then push the EPM 402E along with the piston 314 coupled thereto inthe direction of the arrow 316 (rightward in FIG. 4).

Thus, switching the EPMs 402A-B to the “ON” state caused a cascadingmotion of the EPMs 402A-E, thus applying a motive force to the piston314 and causing it to move. A magnitude of the force applied to the EPM402E and the piston 314, and thus the force that could be applied by thepiston 314 on another object may be dependent on how many of the EPMs402A-E are switched to the “ON” state. If one or more EPMs are switchedto the “ON” state in addition to the EPMs 402A and 402B, the actuationforce applied to the piston 314 may increase. For example, if the EPM402C is switched to the “ON” state such that its north pole (N) andsouth pole (S) face or are adjacent to the corresponding north pole (N)and south pole (S) of the EPM 402B, then the EPM 402C may be repelledaway from the EPM 402B, which is repelling away from the EPM 402A. Forinstance, the force applied to the EPM 402C may be an aggregation of theforce with which the EPM 402B is repelled from the EPM 402A and theforce with which the EPM 402C is repelled from the EPM 402B. As such,the force applied to the EPM 402C causing it to move in the direction ofthe arrow 316 may be larger. As a result, the motive force that isapplied to the piston 314 may increase.

Similarly, if the EPM 402D is switched to the “ON” state such that itsnorth pole (N) and south pole (S) face or are adjacent to thecorresponding north pole (N) and south pole (S) of the EPM 402C, thenthe EPM 402D may be repelled away from the EPM 402C. At the same time,the EPM 402C is repelling away from the EPM 402B, which is repellingaway from the EPM 402A. As such, the force applied to the EPM 402Dcausing it to move in the direction of the arrow 316 may be larger. As aresult, the force that is applied to the piston 314 may increase.

Further, if the EPM 402E is switched to the “ON” state such that itsnorth pole (N) and south pole (S) face or are adjacent to thecorresponding north pole (N) and south pole (S) of the EPM 402D, thenthe EPM 402E may be repelled away from the EPM 402D. At the same time,the EPM 402D is repelling away from the EPM 402C, which is repellingaway from the EPM 402B, which in turn is repelling away from the EPM402A. As such, the force applied to the EPM 402E causing it to move inthe direction of the arrow 316 may be larger. As a result, the forcethat is applied to the piston 314 may increase.

In this manner, the force applied to the piston 314 causing it to movein the direction of the arrow 316 may be progressively increased byprogressively switching more EPMs to the “ON” state. The larger thenumber of EPMs in the “ON” state, the larger the magnitude of the forceapplied to the piston 314, and thus the larger the force that the piston314 applies to other objects.

When the EPMs are switched back to the passive state, they do notexhibit a repulsive force between them and do not cause a motive forceon the piston 314 away from the stop element 312.

In some example implementations, a subset of the EPMs 402A-E could bereplaced with permanent magnets. In these implementations, a permanentmagnet that is replacing a particular EPM may have the particularpolarity of the EPM shown in FIG. 4 when the EPM is switched to the “ON”state. For instance, a permanent magnet may be disposed between twoEPMs. As a specific example, the EPMs 402B and 402D could be replacedwith permanent magnets.

Further, similar to the actuator 300, the actuator 400 may include thespring 318 that couples the piston 314 to the fixed element 320. In thisconfiguration, the spring rate of the spring 318 is such that the forceresulting from one or more of the EPMs 402A-E being switched to the “ON”state could overcome the force of the spring 318 to move the piston 314.When the EPMs that are in the “ON” state are switched back to the “OFF”state, the spring 318 retracts the piston 314 in a direction opposite tothe direction of the arrow 316 (leftward in FIG. 4). To precludeoscillations that could be caused by the spring 318 or an effectivemagnetic spring between the EPMs 402A-E, the actuator 400 may includethe stop elements 322A and 322B that prevents the piston 314 from movingleftward beyond the location of the stop elements 322A and 322B. Inanother example, a damping device may be coupled to the spring 318 so asto mitigate or prevent oscillations of the piston 314.

In an example, similar to the actuator 300, the actuator 400 may operateas a brake actuator. The braking pad 324 may be coupled to the piston314, and as the piston 314 moves, the braking pad 324 may come incontact with the moving object 326, which could be moving linearly(e.g., up and down) or may be a rotary object. When the braking pad 324contacts the moving object 326, the resulting friction therebetweendissipates the kinetic energy of the moving object 326 and slows itdown. The magnitude of the braking force may be based on the number ofthe EPMs 402A-E that are switched to the “ON” state.

In examples, the actuators 300 and 400 may include other components. Forinstance, the EPMs 302A-E or 402A-E may be mounted on or within a tubeto facilitate linear motion of the EPMs. Other components are possibleas well.

FIG. 5 illustrates a side view of a braking system 500, in accordancewith an example implementation. The braking system 500 includes a firstdisk 502 and a second disk 504. The second disk 502 may be coupled to aninput shaft 505 and is thus rotatable therewith.

The first disk 502 may have one or more EPMs 506 disposed on at leastone side face (e.g., front or back side face) or surface of the firstdisk 502. The EPMs 506 may be similar to the EPMs 200, 302A-E, or402A-E, for example. In an example where the first disk 502 has morethan one EPM, the EPMs 506 may form a radial array about the sidesurface of the first disk 502. In this example, the EPMs 506 may beequi-angularly and equi-radially disposed about the side surface of thefirst disk 502. In other words, the EPMs 506 may be disposed at equalradial distance from a center of the first disk 502, and angles formedby any two lines connecting two consecutive EPMs 506 with the center ofthe first disk 502 are equal. This configuration may facilitate havingthe second disk 504 stop at a particular desired location or set oflocations when the EPMs 506 are activated. However, in other examples,the EPMs 506 might not be equi-angularly spaced and might not bedisposed at equal distance from the center of the first disk 502.

The second disk 504 has a plurality of ferromagnetic elements 508 (e.g.,made of magnet steel, or includes permanent magnets and/or EPMs) thatform a radial array about the side surface of the second disk 504 thatfaces the side surface of the first disk 502 having the EPMs 506. Theferromagnetic elements 508 may be equi-angularly and equi-radiallydisposed on the side surface of the second disk 504. The radial distancefrom the center of the first disk 502 to the EPMs 506 and the radialdistance from the center of the second disk 504 to the ferromagneticelements 508 may be equal such that each of the EPMs 506 faces or isadjacent to a corresponding ferromagnetic element 508.

However, in other examples, the ferromagnetic elements 508 might not beequi-angularly and equi-radially disposed about the side surface of thesecond disk 504. For example, the EPMs 506 may be disposed on thesurface of the first disk 502 such that the EPMs 506 form a square shapeinstead of a radial array. Similarly, the ferromagnetic elements 508 maybe disposed on the surface of the second disk 504 such that theferromagnetic elements 508 form a square shape instead of a radialarray. In this example configuration, the attractive forces that maycause a rotational speed of the second disk 504 to change (e.g., slowdown) when the EPMs 506 are activated might be highest at the fourcorners of the square shape.

The first disk 502 and the second disk 504 are juxtaposed on respectiveaxially spaced planes such that an axial gap 510 separates the firstdisk 502 from the second disk 504 as shown in FIG. 5. If the EPMs 506are in the “OFF” state, then no external magnetic field is generatedtherefrom, and no substantial interaction occurs between the EPMs 506and the ferromagnetic elements 508. Thus, the second disk 504 may rotatefreely.

If an electric pulse is provided to the coils of the EPMs 506, then theEPMs 506 switch to the “ON” state and an external magnetic field isgenerated therefrom. When a particular ferromagnetic element 508approaches a corresponding EPM 506, a magnetic circuit is closed and theexternal magnetic field with flux lines 512 attracts the ferromagneticelement 508 to the EPM 506. As a result, the second disk 504 ismagnetically coupled to the first disk 502, and because the first disk502 is stationary, a rotational speed of the second disk 504 may change(e.g., slow down). Thus, providing an electric pulse to the EPM 506effectively applies a braking force on the rotating second disk 504 toslow it down.

As a particular ferromagnetic element 508 rotates away from a particularEPM 506, the magnetic circuit might be opened; however, a subsequentferromagnetic element 508 approaches the particular EPM 506 and anothermagnetic circuit is closed. Therefore, the second disk 504 may remainmagnetically coupled to the first disk 502, and the braking forceremains applied to the second disk 504.

If more than one EPM 506 is disposed on the side surface of the firstdisk 502, then providing electric pulses to the EPMs 506 may increasethe braking force as each EPM 506 may attract a correspondingferromagnetic element 508 that is adjacent to the EPM 506. The largerthe number of EPMs 506 that are switched to the “ON” state, the largerthe braking force. In this manner, the braking force applied to thesecond disk 504 may be progressively increased by progressivelyswitching more EPMs to the “ON” state.

The ferromagnetic elements 508 could take several forms. For example,the ferromagnetic elements 508 could include magnet steel blocks asshown in FIG. 5. However, the ferromagnetic elements could includepermanent magnets, for example.

FIG. 6 illustrates a braking system 600 with ferromagnetic elementsconfigured as permanent magnets 602, in accordance with an exampleimplementation. As shown, the EPM 506 is configured such that, in the“ON” state, its north pole (N) faces or is adjacent to the south pole(S) of the corresponding permanent magnet 602, and the south pole (S) ofthe EPM 506 faces or is adjacent the north pole (N) of the permanentmagnet 602. Therefore, when an electric pulse is sent to the EPM 506, anexternal magnetic field is generated such that the permanent magnet 602is attracted to the EPM 506 and a rotational speed of the second disk504 may change (e.g., slow down).

FIG. 7 illustrates a braking system 700 with ferromagnetic elementsconfigured as EPMs 702, in accordance with an example implementation. Asshown, the EPMs 702 are similar to the EPMs 506, but, in the “ON” state,have opposite polarity compared to the EPMs 506. Particularly, when boththe EPM 506 and the EPM 702 are in the “ON” state, the north pole (N) ofthe EPM 702 faces or is adjacent to the south pole (S) of the EPM 506,and the south pole (S) of the EPM 702 faces or is adjacent the northpole (N) of the EPM 506. Therefore, when an electric pulse is sent toboth the EPM 702 and the EPM 506, an external magnetic field isgenerated such that the EPMs 702 and 506 are attracted to each other anda rotational speed of the second disk may change (e.g., slow down).

As shown in FIGS. 5-7, the disks 502 and 504 face each other such thatan axis of rotation of the second disk 504 may be coincident with anaxis of the first disk 502. However, in another example, the disks 502and 504 may be offset relative to each other.

FIG. 8 illustrates a braking system 800 with a first disk 802 beingoffset relative to a second disk 804, in accordance with an exampleimplementation. The second disk 804 may be coupled to an input shaft 805and is thus rotatable therewith.

The first disk 802 is stationary and may have at least one EPM 806disposed on at least one side face (e.g., front or back side face) orsurface of the first disk 802. The EPM 806 may be similar to the EPMs200, 302A-E, or 402A-E, 506, or 702, for example.

The second disk 804 has a plurality of ferromagnetic elements 808 (e.g.,made of magnet steel, or includes permanent magnets and/or EPMs) thatform a radial array about the side surface of the second disk 804 thatfaces the side surface of the first disk 802 having the EPM 806. Inexamples, the ferromagnetic elements 808 may be equi-angularly andequi-radially disposed on the side surface of the second disk 804.However, in other examples, they might not be equi-angularly andequi-radially disposed about the side surface of the second disk 804.

The first disk 802 and the second disk 804 are juxtaposed on respectiveaxially spaced planes such that an axial gap 810 separates the firstdisk 802 from the second disk 804. Axis of rotation 812 of the seconddisk 804 is offset from an axis 814 of the first disk 802.

If the EPM 806 is in the “OFF” state, then no external magnetic field isgenerated therefrom, and no substantial interaction occurs between theEPM 806 and the ferromagnetic elements 808. Thus, the second disk 804may rotate freely.

If an electric pulse is provided to the coil of the EPM 806, then theEPM 806 switches to the “ON” state and an external magnetic field isgenerated therefrom. When a particular ferromagnetic element 808approaches the EPM 806, a magnetic circuit is closed and the externalmagnetic field attracts the ferromagnetic element 808 to the EPM 806. Asa result, the second disk 804 is magnetically coupled to the first disk802. Because the first disk 802 is stationary, the attraction betweenthe EPM 806 and the ferromagnetic element 808 may effectively apply abraking force on the second disk 804 and may slow it down.

As the particular ferromagnetic element 806 rotates away from the EPM806, the magnetic circuit might be opened; however, a subsequentferromagnetic element 806 approaches the EPM 806 and another magneticcircuit is closed. Therefore, the braking force on the second disk 804may remain applied thereto.

The ferromagnetic elements 808 could take any of the forms discussedabove with respect to FIGS. 5-7. For example, the ferromagnetic elements808 could include magnet steel blocks (see, e.g., FIG. 5), permanentmagnets (see, e.g., FIG. 6), and/or EPMs (see, e.g., FIG. 7).

In FIGS. 5-8, the disks are juxtaposed on respective axially spacedplanes such that an axial gap separates the disks from each other. Inother examples, the disks may be radially disposed relative to eachother.

FIG. 9 illustrates a braking system 900, in accordance with an exampleimplementation. The braking system 900 includes a disk 902 may becoupled to an input shaft 903 and is thus rotatable therewith. Thebraking system 900 further includes at least one EPM 904 mounted to asurface 906. The EPM 904 may, for example, be similar to any of the EPMs200, 302A-E, 402A-E, 506, 702, or 806. The surface 906 could be aperipheral surface of another disk that is stationary.

The disk 902 has a plurality of ferromagnetic elements 908 (e.g., madeof magnet steel, or includes permanent magnets and/or EPMs)circumferentially spaced apart about a periphery or a peripheral surfaceof the disk 902. In an example, the ferromagnetic elements 908 may beequi-angularly spaced about the periphery of the disk 902; however, inother examples, they might not be equi-angularly spaced about theperiphery of the disk 902.

In the example implementation, the disk 902 and the surface 906 aredisposed in a radially spaced juxtaposed relation to one another suchthat a radial gap 908 separates the disk 902 from the surface 906.

If the EPM 904 is in the “OFF” state, then no external magnetic field isgenerated therefrom, and no substantial interaction occurs between theEPM 904 and the ferromagnetic elements 908. Thus, the disk 902 mayrotate freely.

If an electric pulse is provided to the coil of the EPM 904, then theEPM 904 switches to the “ON” state and an external magnetic field withflux lines 910 is generated therefrom. When a particular ferromagneticelement 908 approaches the EPM 904, a magnetic circuit is closed and theflux lines 910 pass through the ferromagnetic element 908 and attract itto the EPM 904. As a result, the EPM 904 may effectively apply a brakingforce on the disk 902 and may slow it down.

A ferromagnetic element 908 is closest to the EPM 904 when theferromagnetic element 908 is at the 9 o'clock position from aperspective of a viewer of the disk 902 in FIG. 9. Therefore, themagnetic circuit may be closed when the ferromagnetic element 908reaches the 9 o'clock position or slightly before the 9 o'clockposition.

As the ferromagnetic element 908 rotates away from the EPM 904 duringrotation of the disk 902, the magnetic circuit might be opened; however,a subsequent ferromagnetic element 908 approaches the EPM 904 andanother magnetic circuit is closed. Therefore, the braking force mayremain applied to the disk 902.

FIG. 10 illustrates a braking system 1000 with an axis 1001 of a firstdisk 1002 being perpendicular to an axis of rotation 1003 of a seconddisk 1004, in accordance with an example implementation. As shown inFIG. 10, the first disk 1002 is disposed in a plane that isperpendicular to a respective plane of the second disk 1004.

The first disk 1002 has at least one EPM 1006 disposed about a peripherythereof. The EPM 1006 could be, for example, similar to any of the EPMs200, 302A-E, 402A-E, 506, 702, 806, or 904. The second disk 1004 has aplurality of ferromagnetic elements 1008 that could include magnetsteel, permanent magnets, and/or EPMs.

The second disk 1004 is configured to rotate with an input shaft 1010.If the EPM 1006 is energized, then it interacts with the ferromagneticelements 1008 as described above with respect to FIGS. 5-9. As a result,a rotational speed of the second disk 1004 may change (e.g., slow down).

In any of the braking systems and apparatuses described above, thebraking force could be alleviated by providing a negative electric pulseto the EPMs to switch them to the “OFF” state.

The actuators, apparatuses and systems described above allow for highswitching speeds as switching occurs by providing an electric pulse. Theelectric pulse has a finite duration (e.g., 200 milliseconds) and couldbe provided in a response time of 100 milliseconds making switchingbrakes on or off quick. Also, the actuators, apparatuses, and systemsdescribed above may have low power consumption because EPMs consumepower when switching, as opposed to continuous consumption of power.

The actuators, apparatuses, and systems described above involve areduced number of moving parts compared to traditional actuators andbraking systems and may eliminate friction between moving parts, thusincreasing efficiency and reliability.

IV. CONCLUSION

It should be understood that arrangements described herein are forpurposes of example only. As such, those skilled in the art willappreciate that other arrangements and other elements (e.g., machines,interfaces, orders, and groupings of operations, etc.) can be usedinstead, and some elements may be omitted altogether according to thedesired results.

While various aspects and implementations have been disclosed herein,other aspects and implementations will be apparent to those skilled inthe art. The various aspects and implementations disclosed herein arefor purposes of illustration and are not intended to be limiting, withthe true scope being indicated by the following claims, along with thefull scope of equivalents to which such claims are entitled. It is alsoto be understood that the terminology used herein is for the purpose ofdescribing particular implementations only, and is not intended to belimiting.

What is claimed is:
 1. An actuator comprising: a piston; a stop element;and a series of electro-permanent magnets (EPMs) comprising at least afirst EPM and a second EPM, wherein the series of EPMs is constrainedbetween the piston and the stop element, wherein each EPM may beswitched between (i) an activated state in which the EPM exhibits anexternal polarized magnetic field and (ii) a passive state in which theEPM does not exhibit an external polarized magnetic field, wherein thefirst EPM and second EPM are arranged such that when both the first EPMand the second EPM are in the activated state, a magnetic pole of thefirst EPM is adjacent to the a like magnetic pole of the second EPM, andthe first EPM and the second EPM exhibit a repulsive force between themcausing a motive force on the piston away from the stop element, andwherein when both the first EPM and the second EPM are in the passivestate, they do not exhibit a repulsive force between them and do notcause a motive force on the piston away from the stop element.
 2. Theactuator of claim 1, wherein the motive force is a first motive force,wherein the series of EPMs further comprises a third EPM, wherein whenthe first EPM, the second EPM, and the third EPM are in the activatedstate, the exhibit a respective repulsive causing a second motive forceon the piston away from the stop element, and wherein the second motiveforce is greater than the first motive force.
 3. The actuator of claim1, further comprising: a brake pad coupled to the piston.
 4. Theactuator of claim 1, wherein the stop element is a hard stop.
 5. Theactuator of claim 1, further comprising: a spring mounted between afixed element and the piston, wherein the spring is configured toretract the piston when the first EPM and the second EPM are in thepassive state.
 6. The actuator of claim 1, further comprising: acompliant element disposed between the stop element and the first EPM.7. The actuator of claim 1, wherein the first EPM and the second EPM arearranged such that when both the first EPM and the second EPM are in theactivated state both magnetic poles of the first EPM are adjacent tolike magnetic poles of the second EPM.